Glucocorticoids upregulate high-affinity, high-density lipoprotein binding sites in rat hepatocytes.

Glucocorticoid hormones (GL) regulate high-density lipoprotein (HDL) plasma concentrations by increasing synthesis and secretion of HDL by the liver. However, little is known about the effect of GL on the uptake and processing of HDL by hepatocytes (HEP). To investigate this question, we studied the effects of dexamethasone (DEX) on the expression of high-affinity HDL-binding sites via the specific binding and internalization of iodine-labeled apolipoprotein E (apo E)-free HDL3 in a culture of rat HEP. Specific binding and internalization of HDL3 decreased by 60% in cells cultured in the absence of DEX for 48 hours. At concentrations of 10(-7) and 10(-5) mol/L, DEX prevented the decrease, maintaining specific binding and internalization versus the control level (at 24 hours). HDL-binding sites with a Kd of 20 micrograms/mL were revealed on the surface of cultured HEP. HEP demonstrated a greater binding capacity in the presence of DEX at concentrations of 10(-7) and 10(-5) mol/L (125 v 45 ng/mg cell protein). The effect of the hormone has demonstrated to be dose-dependent at concentrations between 10(-9) and 10(-7) mol/L, leveling off at 10(-7). Higher concentrations did not induce a further increase in specific binding and internalization. Withdrawal of the hormone from culture medium was associated with a decrease in specific binding of the ligand by 60% in the following 24 hours. To investigate the effect of glucocorticoid deficiency on liver uptake of HDL in vivo, specific binding and internalization were studied in a culture of HEP isolated from adrenalectomized rats (AER) at 2 hours after seeding.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of androgens and somatotropic hormone on the expression of the level of special estrogen-binding protein in the hepatocytes]. / Vliianie androgenov i somatotropnogo gormona na ékspressiiu urovnia osobogo éstrogensviazyvaiushchego belka v gepatotsitakh.

The possibility of direct androgen determination of high unusual estrogen-binding protein (UEBP) level in female rat hepatocytes to the level typical to the males was studied. The direct effect of androgen (A) on the UEBP content in hepatocytes of ovariectomized female rats was shown by estimation in vivo and on hepatocyte culture. It has been revealed that the permissive action of growth hormone (GH) is necessary for normal expression of direct androgen effect. The latter has been stable after cessation of hormone action. High concentration of GH was found to possess positive regulatory effect on the UEBP in hepatocytes of ovariectomized rats. Effect of GH quickly disappeared after hormone withdrawal and was under negative regulation by physiological concentrations of A. It was concluded that A owing to its direct action together with permissive influence of GH is capable of determining stable expression of male phenotype of the UEBP level in hepatocytes of females.

[Role of various hormones of total metabolic action in the expression of sex differentiation of the rat liver by a specific estrogen-binding protein]. / Rol' nekotorykh gormonov obshchemetabolicheskogo deistviia v ékspressii polovoi differentsirovki pecheni krys po osobomu éstrogensviazyvaiushchemu belku.

The effect of some hormones of total metabolic action on a degree of sex differentiation of the liver by a specific estrogen-binding protein (SEBP) was investigated. Insulin administration did not change the SEBP level of the male rat liver. Adrenalectomy and dexamethasone administration caused no significant changes of sex differentiation of the SEBP level in the male and female rat liver. Neither did thyroidectomy cause significant changes in the SEBP level. Dose-related T3 administration decreased reversibly the SEBP level in the liver of adult male rats. The effect of T3 on the SEBP level was preserved after castration or hypophysectomy of males. T3 administration decreased a degree of determination of a raised level of SEBP in the female rat liver by androgens. STH injections were effective mainly in hypophysectomized male rats resulting, on the one hand, in an increase in the level of SEBP and creating conditions, on the other hand, for a decrease in its level caused by estradiol. It has been concluded that thyroid hormones and STH are able to be modulators of adaptive changes of sex differences of the liver by SEBP.

[Estimation of a direct regulatory effect of estrogens on hepatocytes, evaluated according to the change in the level of free estrogen-binding protein in primary cell culture]. / Vyiavlenie priamogo reguliatornogo deistviia éstrogenov na gepatotsity, otsenivaemogo po izmeneniiu urovnia osovogo éstrogensviazyvaiushchego belka v pervichnoi kulture kletok.

Male rat hepatocyte cultures have been obtained. The culturing hepatocytes had a stable level of some morphological and functional properties. A high level of estrogen receptors (ER) and E2-sensitive unusual estrogen-binding protein (UEBP) was found. A direct dose-dependent inhibiting effect of physiological (10(-10)-10(-7) M) concentrations of E2 on UEBP content was established in cell cultures incubated with the hormone for 3 days. Hexestrol (but not cholesterol) was found to exert a direct inhibiting effect. The inhibiting effect of E2 (10(-9) M) was observed after a 24 hour incubation of hepatocytes with the hormone but was less pronounced. In this case a significant increase in UEBP concentration in hepatocytes was noted 72 hours after the removal of E2. It is concluded that physiological concentrations of E2 can exert a direct regulatory influence on certain functions of culturing hepatocytes acting via hepatocyte ER.

[Role of protein biosynthetic processes in realizing the action of sex steroids on the level of specific estrogen-binding protein in the rat liver]. / Rol' protsessov biosinteza belka v realizatsii deistviia polovykh steroidov na uroven' osobogo éstrogensviazyvaiushchego belka pecheni krys.

The authors have assessed the life-span of special estrogen-binding rat liver protein (SEBP) through inhibition of it by long-term administration of cyclohexymid (C1) and have examined how C1 affects the efficiency with which sex steroids influence the level of SEBP. The level of SEBP synthesis was assessed by the changes in the number of SEBP estradiol (E2)-binding sites. The long-term C1 administration in the dose of 100 micrograms suppressed SEBP synthesis by an average of 82.4% with the half-life of SEBP being about 18 hr. Testosterone propionate (TP) and 5 alpha-dihydrotestosterone, but not E2, were found able to mediate enhanced SEBP levels in the liver of ovariectomized female rats. A single 200 micrograms dose of C1 administered 30 min prior to hormone injection caused significant decreases in the efficiency of SEBP-mediated androgen activities in the liver of ovariectomized female rats, in TP-induced stimulation of the SEBP level in the liver of castrated male rats and in E2 inhibitory effect on the SEBP level in the liver of mature males. It is concluded that de novo protein synthesis is necessary for the early manifestation of all the above mentioned effects of sex hormones on the SEBP level. Based on the data regarding the duration of SEBP life and the rate with which it affects the activity of sex steroids it is supposed that in the early stages of hormonally induced manifestations there are changes in biosynthesis of regulating protein rather than in SEBP itself.

[Various mechanisms of the participation of the hypophysis and somatotropin in the hormonal regulation of the level of specific estrogen-binding protein in the rat liver]. / Issledovanie nekotorykh mekhanizmov uchastiia gipofiza i somatotropina v gormonal'noi reguliatsii urovnia osobogo estrogensviazyvaiushchego belka pecheni krys.

A study was made of the role of the hypophysis and STH in the regulation of the level of specific estrogen-binding protein (SEBP) and estrogen receptors (ER) in the rat liver, in the expression of the SEPB-determining effect of androgens (A) and the regulating action of estrogens (E) on the SEPB level. The SEPB and ER content was determined by quantitative methods permitting the differential testing of one E-binding protein from another. Hypophysectomy of males caused a decrease in the SEPB and ER levels. STH administration increased the SEPB and ER levels in the liver of the hypophysectomized males but did not influence the level of these proteins in intact animals. Hypophysectomy of intact and ovariectomized females blocked the SEPB-determining action of A even at early time after operation. Estrogens (E) were capable of producing an inhibitory effect on the SEPB level at early time after hypophysectomy of males. The efficacy of E action after hypophysectomy decreased in parallel with a decrease in the ER content in the liver. The administration of STH to hypophysectomized males resulted in an increase in the ER level and a subsequent reduction of SEPB negative reaction to E. It was concluded that hypophysial factors could produce a direct, sensitizing and permissive for sex steroids action on the SEPB level.

[Role of sex steroids and the pituitary in regulating the level of a specific estrogen-binding protein in rat liver]. / Rol' polovykh steroidov i gipofiza v reguliatsii urovnia osobogo éstrogensviazyvaiushchego belka pecheni krys.

The effects of androgens (A), estrogens (E) and hypophysectomy on the content of an unusual rat liver estrogen-binding protein (UEBP) were studied by the differential quantitative method of the UEBP content measurement. The UEBP content was shown to increase during maturation of male rats. After A injections the UEBP content was high only in the liver of prepubertal but not of mature or immature males. Castration or hypophysectomy of mature males equally caused a decrease in the UEBP content in mature males whereas subsequent administration of A made it completely return to normal. Hypophysectomy of castrated males did not alter the UEBP content. A single injection of E provoked an appreciable reduction in the UEBP level after several days. Administration of A interfered with the inhibitory action of E after simultaneous injection of A and E and recovered the E-induced lowering of the UEBP content upon administration of A following E. Hypophysectomy of castrated males did not affect significantly the UEBP level. The UEBP content was insensitive to the direct action of pituitary factors. The pituitary is necessary for the realization of the effects of E alone but not A. It is suggested that the regulatory role of A consists in the maintenance of the constant optimal UEBP level in rat liver.

[Role of estrogens in the induction and regulation of a specific estrogen-binding protein in the rat liver]. / Rol' éstrogenov v induktsii i reguliatsii urovnia osobogo éstrogensviazyvaiushchego belka pecheni krys.

A study was made of the role of estrogens (E) in the induction and regulation of the level of specific estrogen binding protein (SEBP) in the rat liver using a differentiated quantitative method of its determination. It was shown that E could not replace androgens (A) in the primary determination of the SEPB level, neither did they prevent its A-dependent induction. Multiple administration of 0.4 microgram of estradiol (E2) caused a significant decrease in the SEPB level in intact and castrated male rats as well as in ovariectomized females with the A-induced SEPB level. Multiple administration of even 10 micrograms of E2 did not influence the SEPB level in hypophysectomized males. The rate of development of the E2 effect on the SEPB level of the mature male liver increased with the growth of the dose and duration of hormone administration. The inhibitory effect of E2 was also revealed in a single administration of 10 micrograms of the hormone. In that case the effect was observed after a 3-day lag period, and a maximum decrease in the SEPB level occurred in 6 days. The regulatory negative effect of E2 was reversible. Complete regeneration of the initial SEPB content took place 10-12 days after the development of the maximum effect of E2.

[Androgen induction of specific estrogen-binding protein of rat liver: relationship between the stage of ontogenesis and various endocrine factors]. / Induktsiia androgenami osobogo estrogensviazyvaiushchego belka pecheni krys: zavisimost' ot stadii ontogeneza i riada endokrinnykh faktorov.

A new modification of specific estrogen-binding protein (SEBP) assay in the liver was used to measure the content of this protein at different stages of ontogenesis in male and female rats after administration of testosterone propionate (TP). It was shown that liver capability to form SEBP could be initially programmed by androgens. The crucial period of the SEBP-determining action of androgens in females is not restricted, since potential capability of androgens of primary induction of SEBP may be realized both neonatally and in the course of pubertation. The emergence of SEBP in the liver of males may be the result of natural pre(neo)natal androgenization. Androgens do not play any decisive role in the control of the level of induced SEBP, inasmuch the content of SEBP in the liver of non-pubertal and pubertal males does not appreciably change after TP administration but grows with pubescence. SEBP is capable of long-term existence in the absence of androgens. The presence of the ovaries produces an inhibitory effect on the level of androgen-induced SEBP and the time of its existence after TP discontinuation. Hypophysectomy does not provoke SEBP emergence in pubertal intact and ovariectomized females but prevents its induction with androgens. Adrenal- and thyroectomy produce no influence on the SEBP-programming effect of TP or promote its spontaneous appearance in the same groups of female rats.